- Statement of Changes in Beneficial Ownership (4)

FORM 4 [ ] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES	OMB APPROVAL OMB Number: 3235-0287 Expires: February 28, 2011 Estimated average burden hours per response... 0.5
	Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(f) of the Investment Company Act of 1940

1. Name and Address of Reporting Person * Amello Jason	2. Issuer Name and Ticker or Trading Symbol GENZYME CORP [ GENZ ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director                      _____ 10% Owner __ X __ Officer (give title below)      _____ Other (specify below) CorpContrllr,ChiefAccntOfficer
(Last)          (First)          (Middle) 500 KENDALL STREET	3. Date of Earliest Transaction (MM/DD/YYYY) 4/4/2011
(Street) CAMBRIDGE, MA 02142 (City)        (State)        (Zip)	4. If Amendment, Date Original Filed (MM/DD/YYYY)	6. Individual or Joint/Group Filing (Check Applicable Line) _ X _ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security (Instr. 3)	2. Trans. Date	2A. Deemed Execution Date, if any	3. Trans. Code (Instr. 8)		4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Genzyme common stock (GENZ)	4/4/2011		M		1818.0000	A	$0   (1)	3902.0000	D
Genzyme common stock (GENZ)	4/4/2011		M		1740.0000	A	$0   (1)	5642.0000	D
Genzyme common stock (GENZ)	4/4/2011		M		1447.0000	A	$0.0000	7089.0000	D
Genzyme common stock (GENZ)	4/4/2011		U		2084.0000	D	$74.0000	5005.0000	D
Genzyme common stock (GENZ)	4/4/2011		D		5005.0000	D	$74.0000	0.0000	D

Table II - Derivative Securities Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Trans. Date	3A. Deemed Execution Date, if any	4. Trans. Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Restricted Stock Units	(1)	4/4/2011		M			1818.0000	5/21/2012   (1)	(1)	Genzyme common stock (GENZ)	1818.0000	$0.0000	0.0000	D
Restricted Stock Units	(1)	4/4/2011		M			1740.0000	5/22/2011   (1)	(1)	Genzyme common stock (GENZ)	1740.0000	$0.0000	0.0000	D
Restricted Stock Units	$0.0000	4/4/2011		M			1447.0000	6/16/2013	6/16/2013	Genzyme common stock (GENZ)	1447.0000	$0.0000	0.0000	D
Stock Option (right to buy)	$51.5200	4/4/2011		D			4340.0000	(2)	6/16/2020	Genzyme common stock (GENZ)	4340.0000	$51.5200	0.0000	D
Stock Option (right to buy)	$58.6600	4/4/2011		D			5455.0000	5/21/2009   (2)	5/21/2019	Genzyme common stock (GENZ)	5455.0000	$58.6600	0.0000	D
Stock Option (right to buy)	$68.4800	4/4/2011		D			5220.0000	5/22/2008   (2)	5/22/2018	Genzyme common stock (GENZ)	5220.0000	$68.4800	0.0000	D
Stock Option (right to buy)	$62.1600	4/4/2011		D			4725.0000	5/24/2007   (2)	5/24/2017	Genzyme common stock (GENZ)	4725.0000	$62.1600	0.0000	D
Stock Option (right to buy)	$58.5000	4/4/2011		D			8640.0000	5/25/2006   (2)	5/25/2016	Genzyme common stock (GENZ)	8640.0000	$58.5000	0.0000	D
Stock Option (right to buy)	$62.9800	4/4/2011		D			9300.0000	5/26/2005   (2)	5/26/2015	Genzyme common stock (GENZ)	9300.0000	$62.9800	0.0000	D
Stock Option (right to buy)	$43.9000	4/4/2011		D			11590.0000	5/27/2004   (2)	5/27/2014	Genzyme common stock (GENZ)	11590.0000	$43.9000	0.0000	D
Stock Option (right to buy)	$48.3800	4/4/2011		D			4000.0000	12/23/2003   (2)	12/23/2013	Genzyme common stock (GENZ)	4000.0000	$48.3800	0.0000	D

Explanation of Responses:
( 1)	The vested restricted stock units were scheduled to be released on 5/22/2011 and 5/21/2012.
( 2)	This option, which provided for vesting 20% at grant and 20% annually over four years, was cancelled upon the consummation of the sanofi-aventis tender offer in exchange for a payment representing (A) an amount of cash equal to the excess of $74.00 over the exercise price of the option, multiplied by the total number of shares subject to such options, and (B) one contingent value right (CVR) per cancelled option.

Reporting Owners
Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Amello Jason 500 KENDALL STREET CAMBRIDGE, MA 02142			CorpContrllr,ChiefAccntOfficer

Signatures
Susan P. Cogswell, Attorney-in-Fact		4/6/2011
** Signature of Reporting Person		Date

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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